1. Field of the Invention
This invention relates generally to gas sampling bags, and is concerned in particular with a new and improved fitting for sealing and gaining access to an opening in the bag wall.
2. Description of the Prior Art
The lowest cost and most commonly used gas sampling bags are fabricated from Tedlar with polypropylene access fittings. However, the reusability of such bags is limited due to gas adsorption on the surface of the Tedlar material, which could adversely affect sensitive testing of subsequent gas samples.
All perfluoroplastic gas sampling bags, i.e., those fabricated from perfluoroalkoxy (PFA), fluorinated ethlylene propylene (FEP) or polytetrafluorethylene (PTFE) are also available, but at a much higher cost, due primarily to their complicated and expensive access valves that are typically machined from perfluoroplastics or stainless steel. These materials resist surface adsorption of the gases being sampled, thus making is possible to use the sampling bags repetitively. However, this advantage is compromised by the limited septum life of the access fittings.